Devilduck, unlike most model airplane kits these had a fuselage ( body) of solid balsa wood about 1 1/4" X 2" X 8" which is quite a chunk of balsa! This was then hollowed out by machine from the factory on bottom side with slot about 3/4" wide by about 4" long hence the moniker "hollow log"

A kit typically would loook much like this.

Robert